1. Field of the Invention
The present invention relates to a sample preparation method and apparatus for preparing a sample by etching processing using a focused ion beam.
2. Description of the Related Art
As a method of analyzing internal structure and defects in a semiconductor device or the like, there is known a cross-section processing and observation method, in which a focused ion beam is used for cross-section processing of a sample to expose a cross-section including a desired structure or a defect and a scanning electron microscope is used to observe the cross-section. According to this method, a desired observation target inside the sample can be exposed with pinpoint accuracy, and hence the structure or the defect can be observed quickly.
As a method for exposing a desired observation target, there is disclosed a method of repeatedly performing cross-section processing and cross-section observation, and finishing the cross-section processing at the timing when an observation target appears in a cross-sectional observation image (see JP-A-2009-204480). According to this method, a cross-section including a desired observation target can be exposed accurately.
As another analysis method, there is also known a method of preparing a sample piece including a desired observation target from a sample by a focused ion beam and observing the sample piece by a transmission electron microscope. According to this method, an observation target can be observed by the transmission electron microscope with a high resolution.
In the case of using a focused ion beam to expose a cross-section of a semiconductor device or prepare a sample piece, it is important to process a cross-section along an arrangement direction of a device pattern in a semiconductor wafer.
In the cross-section processing and observation method, the structure or defects are observed from an observation image of a cross-section including a device pattern, and hence it is necessary to expose the cross-section along the arrangement direction of the device pattern. Further, in the preparation of the sample piece, the internal structure of the sample piece is analyzed by transmission electron microscope (TEM) observation, and hence it is necessary to prepare a sample piece which has a desired structure inside, and is along the arrangement direction of the device pattern.
However, in recent years, the device pattern has become finer along with densification and reduction in size of semiconductor devices. Thus, it has been difficult for the conventional method to check the arrangement direction of the device pattern by observation and form the cross-section along the arrangement direction of the device pattern.